confused about performance
Hi folks, I just bought a pair of AMD64 systems for a work project,
and I'm confused about the performance I'm getting from them. Both are
identically configured Dell Dimension C521 systems, with Athlon 64 X2
3800+ CPUs and 1 GB RAM.
On one I installed using the Etch (4.0r0) i386 netinst CD, then upgraded
to Lenny. This one's running linux-image-2.6.21-1-686.
On the other I installed using the current (as of 2007-06-13) Lenny d-i
amd64 snapshot netinst CD. This one's running linux-image-2.6.21-1-amd64.
The one with the x86 userspace and 686 kernel is faster than the one
with x86_64 userspace and amd64 kernel. The difference is consistently
a few percent in favor of x86 over x86_64.
My only benchmark is compiling our internal source tree (mostly running
gcc, some g++, flex, bison, etc). We're using gcc-4.1 and g++-4.1.
I've tried it with a cold disk cache and hot disk cache, in both cases
x86 is faster than x86_64.
I was expecting a win for 64 bit. What's going on here?
"We're building a machine that will be proud of us."
-- Danny Hillis, Thinking Machines Corporation, 1982